1. Field of the Invention
The present invention relates to watthour meter adapter assemblies, and, more particularly, to a new and improved lock arrangement for securing a watthour meter to an adapter to make removal of the watthour meter from the assembly more difficult than is normally the case.
2. Description of the Prior Art
There are today in the field a large number of individual electrical service installations for residences, and the like, which have a two-wire service. The industry, in many instances, utilizes two-wire bottom connected watthour meters to measure the electrical power consumption. The ever increasing reliance of the consumer on electrical appliances in the home has resulted in an increased demand for electrical power, and the utilities recognize today that in the future, it will be necessary to replace many of the two-wire services with three-wire service. This, of course, also requires the installation of a new three-wire meter for electrical power measurement purposes.
In anticipation of the phasing out of two-wire systems over a period of years, the utilities would prefer in most cases to replace the two-wire meters with three-wire meters because of the relatively long life of the meters used in the field today, such three-wire meter being used to measure the power input over the two-wire lines until such time as conversion is ultimately made to a three-wire service. The utility industry, therefore, will frequently use a watthour meter adapter assembly which permits a modern socket-type watthour meter designed for three-wire service to be adapted for use in the measurement of the electrical power input over the two-wire service without requiring a change in the service wiring at the installation.
One such adapter assembly which may conveniently provide for such versatility and convertability includes a plurality of jaw-like contacts which electrically and mechanically cooperate with bayonet contacts formed on the watthour meter, and which are also directly connected to adjustable lug type terminals that connect the adapter to an electrical distribution system.
An annular clamping member clamps the watthour meter to the adapter assembly and maintains the bayonet contacts in engagement with the jaw-like contacts. A suitable locking mechanism tightens the clamping member in position. However, in known assemblies such locking mechanism is readily accessible from the front of the meter and thus easily released.
Since such adapter will accept either a three-wire or a two-wire instrument, an installer may inadvertantly replace a three-wire meter with a two-wire meter under the assumption that a two-wire meter is normally required for two-wire service. In such instances, the meter will not provide a record of the electricity used by the consumer.
To prevent against such inadvertance, approaches have been undertaken in the field to frustrate the substitution of a two-wire watthour meter on an adapter assembly by making normal removal and substitution operations for the meter much more difficult to perform through the provision of a locking device which holds the meter in place on the adapter assembly. By increasing the difficulty needed to remove or substitute a meter to a point that is greater than would otherwise be expected, it is intended that the installer will be alerted to the fact that the installation includes a three-wire watthour meter, and therefore, the risk of replacement of the three-wire meter with a two-wire meter is substantially reduced.
One example of a prior art locking device for this purpose is disclosed in the U.S. Pat. No. 3,636,498 of Alexander McQuarrie wherein a watthour meter adapter assembly is provided with a ring-like clamping member which clamps a watthour meter base to the adapter assembly and an L-shaped latching device having a shaft portion which extends through an aperture in the clamping member to prevent its release. Such arrangement, however, is rather complicated and expensive in construction. Moreover, the dimensioning of the aperture in the clamping member and the shaft portion of the locking device may be critical to the assembly and removal of the locking mechanism as well as to accomplishing the intended purpose of preventing a serviceman from easily removing the watthour meter from the adapter base.